The present invention relates generally to systems for draining water away from a generally flat substrate, and more particularly to a drainage member that is designed to be located beneath an upper layer of material, such as artificial turf, synthetic turf or the like, for draining away water that seeps through such upper layer.
It has been known for some time that natural grass can be replaced with artificial or synthetic turf in many environments. In general, artificial turf requires considerably less maintenance than natural grass or sod, and it can often be used in locations where natural grass cannot be grown. Artificial turf systems can take various forms, and one typical system is disclosed in U.S. Pat. No. 5,601,886 in which the artificial turf is fabricated in a tufting machine so that artificial turf filaments penetrate backing material.
While there are many applications for artificial turf, perhaps the most common are on athletic fields such as indoor and outdoor soccer fields or football fields, and on golf greens. Typical applications of this type are disclosed, for example, in U.S. Pat. Nos. 5,779,393; 5,976,645; and 6,221,445. When the artificial turf system is used in an outdoor environment where it is subjected to rain and other sources of water, the system must have some provision for draining water that would otherwise accumulate on top of, underneath, and within the filaments of the artificial turf.
One type of drainage system that is frequently used with artificial turf is a thick layer of sand or other small loose particles through which water can drain, such as the system disclosed in the aforesaid U.S. Pat. No. 6,221,445. While these drainage systems and others like them are adequate for properly draining the water away from the artificial turf, they are costly, both from the standpoint of the costs of the materials themselves as well as the significant labor costs involved in properly installing the drainage system.
There has been some experimentation in trying to substitute less expensive known drainage systems that are formed from a plastic material, such as polystyrene, polyethylene or the like, and that include projections with spaces therebetween to create drainage passageways for draining away excess water. However, it was found that these drains could undergo significant expansion when they are exposed to typical heat conditions that are often encountered by artificial turf systems. When these drainage systems were employed in the long lengths normally required for large areas of artificial turf, such as football or soccer fields, the expansion problem was exacerbated to the point that it created wrinkles and other malformations of the artificial turf which are difficult and expensive to correct.
In accordance with the present invention, a drainage member is provided that is considerably less expensive than known drainage systems, and avoids the problem of undue expansion of the drainage member.